In the world of high-speed auto racing, extreme demands are placed on both car and driver. Nowhere is this more true than in the realm of high-speed, short-duration racing, such as drag racing. In these races, drivers command high performance vehicles to accelerate through one-quarter mile of roadway in approximately seven seconds, reaching speeds of over 200 miles per hour. Frequently, the drivers and vehicles are so competitively matched that as little as one thousandth of one second can make the difference between winning and losing a race. Accordingly, drivers look for any way to improve their performance and consistency, even if only by the smallest of margins.
In this regard, drivers train heavily on effective gear shifting. During a typical, seven second racing interval, the driver must normally shift through four or five gears. Indeed, in the professional drag racing circuit, driving skill plays a significant role in the outcome of the race. Not only should the driver be able to shift quickly and cleanly, but the driver should also shift at the appropriate engine speeds to extract the maximum power and racing speed from the vehicle. To be sure, the characteristics of any given vehicle (e.g., aerodynamics, etc.) combine to define a maximum performance curve for each gear of that vehicle. This performance curve, in turn, defines the optimum engine speed for each gear at which the driver should shift in order to effect maximum speed from the vehicle. In addition to rote practice, however, drivers also look to instrumentation or other driving aids to help them properly time and execute these critical shifts at the appropriate points along the power curves.
Of course, tachometers have long been known to provide a vehicle operator with an instantaneous display of engine speed. Other engine speed sensing devices are known to provide what can be generally referred to as "RPM switches." These RPM switches are typically individual, stand-alone units adapted to monitor the engine speed and signal or otherwise act upon the detection of certain desired engine speeds. RPM switches are used in a variety of applications such as controlling nitrous oxide injectors, limiting the engine RPM, controlling system ignition timing, and operating shift lights, just to name a few. An RPM switch may be dedicated to control a shift light, which illuminates at certain preprogrammed engine speeds to prompt the driver to shift gears. Shift lights may be provided in connection with an RPM switch imbedded within the tachometer or in a separate control box. These current art devices basically use the logic of an RPM comparator to compare the engine's instantaneous RPM with a preselected Shift Point (SP) RPM. Whenever the preselected shift point RPM for the first shift (i.e., SP1) is reached, the Shift Light Indicator is energized and the circuit logic shifts the RPM comparator onward to the Second Shift Shift Point RPM (SP2).
This sequential pattern of triggering the Shift Light display when the Shift Point RPM is reached and then shifting the RPM comparator value to that RPM preselected for the next Shift Point occurs for each successive gear change.
There are two main problems with this control logic used in all existing art:
1. Over-Rev at launch:
As the race car leaves the starting line at max power it is easy for the tires to lose traction and the engine to achieve a high enough RPM to trigger the Shift Point setting for the first shift (SP1). When this occurs, the Shift Light will be energized "ON" and the control logic will now be sequenced to be looking for the second Shift Point RPM while the car will still be in first gear. This poses a problem for the driver in that for this race his Shift Point RPM logic will now always be one preselected Shift Point RPM ahead of the Shift Point he will be looking to make.
2. Shifting too early:
Occasionally, whether because of a loss of traction or just a slight error in timing, a driver will shift early before the engine gets up to the desired RPM shift point. This early shift is often called a "Short Shift."
When a Short Shift occurs, the preselected Shift Point RPM was not achieved thus the Shift Light would not have been energized and very importantly, the RPM comparator logic would not have been switched onward for the next preselected Shift Point RPM value.
In this case, the Shift Light control logic would now be one preselected Shift Point RPM behind from the shift the driver was looking to make for the rest of that race.